2-methylhydroquinone

Endpoint summary

Description of key information

In an In-vitro Skin Corrosion test on EpiDerm tissues (OECD Test No. 431: In vitro skin corrosion: reconstructed human epidermis (RHE) test method) the average viability of affected tissues was 7.2% of negative control average value after 3 minutes of treatment. The viability after 3-minute exposure is < 50 % and < 25 %. Therefore, methylhydroquinone is classified as corrosive, sub-category 1A.

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Endpoint:

skin corrosion: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

16.03.2018 - 29.03.2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 431 (In Vitro Skin Corrosion: Reconstructed Human Epidermis (RHE) Test Method)

Version / remarks:

Adopted: 29th July 2016

Deviations:

yes

Remarks:

In the MTT test there were used only two tissues per each time interval for the positive control (PC) and negative control (NC).

GLP compliance:

yes (incl. QA statement)

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Cell source:

foreskin from a single donor

Source strain:

not specified

Justification for test system used:

non-animal test

Vehicle:

water

Details on test system:

MTT Test
Test item application: 25 mg of the test item was placed directly atop to the moistened tissue and it was spread to match size of the tissue.
Controls:
Negative control - 50 μL H2O tested with every exposure time
Positive control - 50 μL 8N KOH tested with every exposure time

Procedure: After delivery, tissues were pre-incubated overnight to release transport stress related compounds and debris. After overnight pre-incubation, medium was replaced to fresh one and tissues were topically exposed to the test item for 3 (room temperature) and 60 minutes at culture conditions (37±1°C, 5±1 % CO2, humidified). In each time interval three tissues were used per test item (C1), two tissues for the positive control (PC) and two tissues for negative control (NC). In additional freeze-killed tissues were used. In each time interval two tissues were used for the test item (C1) and two tissues for negative control (NC). After exposition, tissues were thoroughly rinsed and blotted to remove the test item/controls.
After that, tissues were transferred to 24-well plates containing MTT medium (1 mg/mL) and incubated at culture conditions for 3 hours. After MTT incubation, the blue formazan salt (formed by cellular mitochondria) was extracted with 2.0 mL/tissue of isopropyl alcohol for 2 hours at room temperature and shaking. Optical density of the extracted formazan was determined using a spectrophotometer at 570 nm.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

yes, concurrent MTT non-specific colour control

Amount/concentration applied:

25 mg

Duration of treatment / exposure:

3 min./ 60 min.

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

after 3 min.

Value:

7.2

Negative controls validity:

valid

Positive controls validity:

valid

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

after 60 min.

Value:

-31.6

Negative controls validity:

valid

Positive controls validity:

valid

Direct MTT reduction - functional check in tubes

25 mgof the test item was addedto 1.0 mL of MTT medium. Suspension was incubated for 1 hour (37±1 °C, 5±1 % CO₂, humidified). The test item changed colour of MTT medium from red to dark purple.

The test item reduces MTT directly.

Colour interference

After addition of test item the water changed colour to light pink and in isopropyl alcohol there were not observed any change of colour. The change of colour in water was not significant so it was no need for additional controls (colorant control).

Interpretation of results:

Category 1A (corrosive) based on GHS criteria

Conclusions:

The test item methylhydroquinone should be regarded as corrosive, sub-category 1A since it was corrosive in an In-vitro Skin Corrosion test on EpiDermTM tissues (OECD Test No. 431: In vitro skin corrosion: reconstructed human epidermis (RHE) test method).

Executive summary:

In an In-vitro Skin Corrosion test on EpiDerm tissues (OECD Test No. 431: In vitro skin corrosion: reconstructed human epidermis (RHE) test method) the average viability of affected tissues was 7.2% of negative control average value after 3 minutes of treatment. The viability after 3-minute exposure is < 50 % and < 25 %.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (corrosive)

Eye irritation

Link to relevant study records

Reference

Endpoint:

eye irritation: in vitro / ex vivo

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance is classified as skin corrosion, leading to classification as serious eye damage (Category 1)

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irreversible damage)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Justification for classification or non-classification

Methylhydroquinone is classified to be corrosive to the skin and the eyes based on an OECD guideline test 431 (In vitro skin corrosion: reconstructed human epidermis (RHE) test method). It is therefore also considered as irritant to the respiratory tract.